1. Field of the Invention
The present invention pertains to a spread spectrum type portable telephone apparatus which uses a spread spectrum scheme and which is used in digital radio communications with automobile telephones and portable telephones, etc.
2. Prior Art
The spread spectrum scheme in the present invention is a scheme wherein, by means of a code division multiplexing access (CDMA) mode, transmission data are spectrum spread, subjected to multiplexing processing, and transmitted as radio signals. Known transmitters and receivers in spread spectrum type portable telephone apparatuses are made so that, even when in the wait state for monitoring a pager channel, circuits are always used which have the same broad bands and high speeds as the communications channels. An example of such a conventional spread spectrum portable telephone apparatus is diagrammed in FIGS. 3 and 4. FIG. 3 is a block diagram that depicts the configuration of the base station transmitter in a conventional spread spectrum portable telephone apparatus. FIG. 4 is a block diagram that depicts the configuration of the mobile unit receiver in a conventional spread spectrum portable telephone apparatus.
First of all, with reference to FIG. 3, the configuration of the bas e station transmitter in a conven-tional spread spectrum type portable telephone apparatus is described. In FIG. 3, 201 is a base station transmitter which makes radio transmissions to a plurality of mobile units. 202 is a frame assembler circuit that takes the transmission data from each line or the paging information and assembles that into a frame format together with control information. 203 is a spread code generator circuit that generates spread codes (specific to each system) which are allotted to each of the apparatuses that spread transmission data. 204 is a multiplier that multiplies the transmission data or paging data by the spread codes.
Moreover, 205 is an adder circuit that takes spread transmission data or paging information and puts that together into one structure; 206 is a band limiting filter that waveform shapes the data output from the adder circuit; 207 is a DA converter circuit that converts the data output from the band limiting filter to an analog signal; 208 is a mixer that modulates the carrier wave signal with the transmission data and outputs a radio signal; 209 is a carrier wave generator circuit that generates a carrier wave signal for transmitting the radio signal; 210 is a power amplifier circuit that amplifies the power of the radio signal in order to transmit it; and 211 is a radio signal transmission antenna.
The operation of the base station transmitter unit of a conventional spread spectrum portable telephone apparatus will be described with reference to FIG. 3. First of all, in the base station transmitter unit 201, the transmission data on the various lines, i.e., 1, 2, . . . , n, that are sent through the communications channel are assembled by the frame assembler circuit 202 into a transmission frame format to which has been attached various kinds of control information, etc., thereafter multiplied in the multiplier circuit 204 with a spread code generated by the spread code generator circuit 203 and spread into a broad band signal.
Furthermore, the spread transmission data are put together into one structure by the adder circuit 205, the output of which is waveform shaped by the band limiting filter 206, and converted into an analog signal by the DA converter circuit 207. The transmission data that have been converted to an analog signal are converted (modulated), in the mixer 208, to a modulated signal having the frequency of the carrier wave that is output from the carrier wave generator circuit 209. [This signal] is then amplified by the power amplifier circuit 210 and radio transmitted from the transmission antenna 211.
Furthermore, the paging information that is sent by the paging channel for the purpose of calling a mobile unit, after being programmed into a transmission frame format, with various control information, etc., attached thereto in the frame assembler circuit 202, is multiplied by a spread code having the same speed as the communications channel and generated by the spread code generator circuit 203, for paging channel use, in the multiplier 204.
The spread paging channel signal is band limited by the band limiting filter 206 that has the same band as the communications channel, converted to an analog signal by the DA converter circuit that is the same as [for] the communications channel, converted (modulated) by the mixer to a modulated signal having the same carrier wave frequency as [for] the communica-tions channel that is output from the carrier wave generator circuit 209, amplified by the power amplifier circuit 210 that is common with the communications channel, and radio transmitted from the transmission antenna 211.
Next the configuration of the mobile unit receiver of a conventional spread spectrum portable telephone apparatus will be described with reference to FIG. 4. In FIG. 4, 212 is a mobile unit receiver that receives radio signals from the base station transmitter 201. 213 is a reception antenna therefor. 214 is a low noise amplifier circuit that amplifies the reception data (or paging information) received from the reception antenna 213. And 216 is a detection circuit that detects and demodulates the reception data using a signal having the station generated frequency.
Moreover, 215 is a station generator circuit that generates a signal having the station generated frequency. 217 is an AD converter circuit that converts the detected analog signal to a digital signal. 218 is a reception filter that waveform shapes the digital signal received. 219 is a correlator that despreads (correlates) the waveform shaped digital signal using a spread code. 220 is a spread code generator circuit that generates a spread code (specific to each system) that is apportioned to each apparatus. 221 is a frame resolving circuit that extracts reception data from the frame format. And 222 is a controlling means for controlling the spread code generator circuit 220.
Next the operation of the mobile unit receiver of a conventional spread spectrum portable telephone apparatus will be described with reference to FIG. 4. In the mobile unit receiver 212, the incoming call status is monitored so that the paging channel is received while waiting, and the communications channel is received during communications. First, the operation while waiting will be described. The paging channel signal that is captured by the reception antenna 213 is amplified by the low noise amplifier 214, detected and demodulated, in the detector circuit 216, by means of a signal having the station generated frequency that is output from the station generator circuit 215, and converted into a base band signal.
The paging channel signal, after being converted to a base band signal, is converted to a digital signal through the AD converter circuit 217 that is the same as [for] the communications channel, and is waveform shaped by the reception filter 218 that is the same as [for] the communications channel. The waveform shaped paging channel signal is despread (correlated) in the correlator 219 using the spread code, and the paging information is extracted through the frame resolving circuit 221.
The operation of a call in a case where, during paging channel reception, a call to said mobile unit has been detected will be described next. The circuits of the mobile unit receiver 212 that are used for receiving the communications channel signal are the same circuits as are used for receiving paging channel signals. More specifically, the received communications channel information is received and processed through the same circuits and over the same paths as is the paging channel signal, and the received data are extracted by the frame resolving circuit 221. Accordingly, any further detailed description hereof is omitted inasmuch as it is the same as the description given above.